COAL IN NEW ZEALAND. No. 2.

Otago Witness, Issue 749, 7 April 1866, Page 7

COAL IN NEW ZEALAND. No. 2.

The first article which we extracted from the " Reports and Awards of the Jurors," as to the New Zealand Exhibition, gave a general view of the distribution of Coal throughout New Zealand. We now extract from Appendix A. which contains a report by Dr. Hector, Colonial Geologist, and Mr W. Skey, analytical chemist to the Geological Survey. As there is much misapprehension of the true nature and relative value to be attached to the various kinds of coal found in New Zealand, arising principally from the fact that their geological age cannot be definitely compared with the true coal formation in the Northern Hemisphere, it is nece:*sary to preface this account of the coal exhibits by a brief explanation of the views which are at present accepted concerning the nature and origin of carbonaceous deposits. The term "coal" receives a vague application to a variety of substances, which have been produced from the vegetation of past geological ages, by a slow chemical and mechanical change, and which is one of the forms of that process oi decay by which all organised Eubstances revert to their inorganic elemtnts. The principal circumstances which determined the production of coal rather than humus or vegetable mould, seem to have been the exclusion of the atmosphere from the vegetable matter, before true decomposition had commenced. This exclusion was effected when a deposit of sediment, especially that of argillaceous character, was promptly superimposed upon it in consequence of the depression under water of the area on which the vegetable matter had accumulated. According to chemist?, the process by which vegetable matter — which consists essentially of carbon, hydrogen and oxygen — has been converted into coal, depends on the elimination of the oxygen or incombustible element at the expense of a certain portion of the two former. The process is progressive, and the value of the resulting coal depends on the extent to which the concentration of those elemtnts which give it value as fuel has been effected.

In nature, therefore, a very complete series of substances represents the various stages of this process, — thus we have wood, peat, jet, lignite, bituminous coal, freeburning coal, and anthracite. In these we have a series, step by step, increasing in the per centage of carbon, and consequently decreasing in the per centage of hydrogen and oxygen — the last-mentioned substance, anthracite, being nearly pure carbon ; and it is hardly necessary to remark that the carbon and hydrogen are the useful heatgiving constituents of coal, while the presence of oxygen greatly decreases its calorific powers. The rapidity by which this process has progressed in any given case will depend on various circumstances — such as the manner in which the vegetable matter was deposited, the degree to which ordinary decomposition had progressed previous to the covering up of the mass, and the amount of pressure and temperature to which it has been subsequently subjected. But all of these conditions are apparently subordinate to the time during which the above process has been iv operation, or what is the same thing, to the geological age of the deposit. Deposits of coal evidently indicate the presence of dry land upon which the vegetation flourished, and from its peculiar botanical character, as well as the frequency and ease with which it had been submerged, it would appear that this land was of a low esturme character, or at any rate was in close proximity to the sea or to large lakes. Consequently, wherever such circumstances existed, coal formations would in all probability result. The popular opinion is, however, that deposits of useful coal are confined to what are known as the " coal measures," at which period of the earth's history conditions highly favorable to the luxuriant growth and preservation of vegetable matter appear to have been more universally distributed on the surface of the globe than at any other epoch of which we have legible records.

Valuable sources of coal, which present only slight differences from true coal, may, however, be found in the newer formations, such as the Oolitic and Cretaceous systems, whilst even the Tertiary strata are remarkable for their local deposits of coal of various degrees of usefulness.

The term " coal proper" is commonly applied to those substances found in the true carboniferous system, while those of a more recent date have been denominated by such vague terms as lignite and brown

coal, the former having reference generally to those varieties presenting evident woody structure, whilsWhe latter is used by the Germans to include all varieties which are of more recent geological age.

Using the word coal in its widest signification, the varieties which will be referred to in this report may be conveniently divided into two groups, viz. : —

(1.) Lignite and Brown Coal ; (2.) Noncaking and Caking Bituminous Coal — which distinctions are founded on both their physical and chemical characters, and a consideration of their geological age. Lignite deposits occur iv what are obviously old lake basins, scattered over the surface of the primitive slate rocks in the interior of New Zealand. They bear evident signs of having been formed from drift wood, as fragments of trees are of freiuent occurrence in which the woody tissue is still quite perfect. In some of those deposits in the Province of Otago it is possible to recognise, among: other woods, that of a species of Fagus, or so called Birch, of New Zealand, a genus of tree which still predominates in the primeval forests of the western seaboard.

These lignite deposits are of recent tertiary age, being only overlaid by the newer drifts in the form of brick clays, ferruginous gravels, silts, and shingle terraces.

Lignites are u?ed as fuel in several localities in the interior of Otago, and are not commonly distinguished from the brown coals proper. In some cases they burn with great facility, owing to a large quan tity of fossil resin which is disseminated throughout them.

In certain deposits of equivalent age to those containing the lignites, the stems and trunks of trees cemented with eilicious chert, are of frequent occurrence, and there is evidence from other sources to prove that the period of this depr sit was characterised by an extensive distribution of the forest growth over the mountainous regions of the islands, arising from a great increase of altitude due to a general elevation of the land.

The Brown Coal Formation underlies the marine tertiary sandstones and limestones which are so extensively developed throughout New Zealand, but it also occurs in the la r ge basin like valleys of the interior, where it always forms the fljor or base of the upper tertiary series, which usually rests on it unconformably. It is the most universally distributed coal formation of New Zealand, and in Otago Province for instance, there is no di-trict that is not within easy distance of a deposit of this coal, or of lignite, so that it has proved most useful as fuel to the miners on the Goldfields, where the supply of timber is so deficient. Notwithstanding this wide d'stribution. these deposits appear to be detached and local in character, and not portions of an extended and continuous formation. They have, nevertheless, been involved in the later dislocations of the older rocks, a circumstance which has no doubt caused them to vary in their composition and value as fuel. The character and thickness of the brown coal formation varies very much. As a general rule, the lower part is mostly conglomeritic and arenaceous iv character, passing upwards into argillaceous Btrata, which in some districts have the nature of true plastic clays. Its largest development in the Province of Otago is on the Ea9t Coast, northward from the Clutha or Molyneux River, where it extend* continuously at least over 45 square miles, forming hills from 500 to 1000 feet in height, which are broken into sharp ridges by the out-cropping beds of conglomerate and sandstone. This formation is scarped by the sea for many miles, so that it is probably only the remnant of a much larger basin that stretched to the eastward. In this section maoy seams of good coal are fo.ind, some of them ranging from 18 to 23 feet in thickness — the estimated aggregate thickness beins 56 fret. These coal seams have generally a roof of tough shale, but only in few cases do they rest on a stratum of fire-clay, the floor being more usually of a grit or fine-grained conglomerate. In other parts of Otago and in the Province of Southland, this formation is also extensively met with, but probably its greatest development is in the North Island, where, according to Hochstetter and Crawford, it underlies the immense plains of marine tertiary strata which form so large a portion of the surface.

Brown coals differ in several important particulars from true coal, though whether these differences are essential to their geological age is a question still to be determined. The most characteristic difference consists in the quantity of water which they contain in combination— often reaching to 30 per cent., from 10 to 20 per cent, being usual, while true coal seldom contains more than 5 per cent. This defect should not be overlooked in an estimate of their value ; for take an example with 10 per cent. — the fact that every ten tons of coal contain one ton of water does not represent the magnitude of the loss, as this water absorbs a large quantity of the heat produced by the combustion of the nine

tons of fuel, in the co aversion of the one ton of water into steam.

Notwithstanding its defects, brown coal .will be yet largely used in this colony both for domestic and other purposes. The disagreeable smell of creosote and sulphurous gag which some varieties give off in burning, and which forms the strongest objection to their being adopted as a domestic fuel, can be altogether escaped by burning it in a stove possess" ng a good draughtadapted for its use.

It can also be used in this manner more economically than in an open fiie- place, and in small stoves of the above descrip'ioa a very inferior quality of coal to that which New Zealand possesses is largely consumed in Germany for household purposes.

The principal defect of brown coal as & fuel for the purpo*e of ra : sing steam, arises from its greater bulk in proportion to its weight, and the reduction of its calorific power, owing to the large quantity of water which it contains, as previously explained. Both these disadvantages can only be remedied by the use of more than usually capacious furnaces, with close fire bars and wide air passages. In the case of stationary engines this is of course effected, and after a short experience I have little doubt that the stokers would prefer the brown coals to the more bitumit.ous varieties, as they form no clinker, and give a steadier heat with a much less amount of labor.

They can never come, however, into use for steamers or for locomotive engines, where economy of space is the main consideration, as, judging from practical experiments, as well as from examination in the laboratory, the effective power o( the bituminous coal is one-fourth more than that of of an equal bulk of brown coal. In other words, the quantity of brown coal required to do the same work as 20 tons of bituminous coal would require for s'oragc the same space that would contain 25 ton. of the better fuel.

As several patents have been taken out for the purpose of preparing a condensed fuel for steam purposes, from varieties of non-caking coals, it is possible that some adaptation of this process might be applied to the brown coals, by which the water they contain would be driven off and replaced by a small quantity of bituminous matter, that would re cement them in the form of solid bocks of convenient s"ze and density. Much might also be effected towards improving the form of furnaces, ia order to suit the peculiarity of the fuel.

The gas derived from the inferior varieties of brown coal is of very inferior quality, and deficient iurichhydro-cirbon ; all the varieties can, however, be highly recommended for the purpose of burning bricks and lime.

The Duties on Foreign Wines is England. — The Memorial Diplomatique publishes the following intelligence :—: — " Our Vienna letters informed us that the chief difficulty which had retarded the conclusion of the commercial preliminaries between Austria and England consisted in the hesitation of the St. James's Cabinet to lower its tar'ff in favor of Austrian Mr Gladstone, foreseeing that France, in virtue of her treaty with England, would im nediatcly claim for her own wines all the advantages that might be accorded to the Austrian, proposed to place those of the latter ountry in the second class of t-ie English tariff, which includes potable liquors whose alcoholic strength reaches 25 deg. On examination, the concession was found to be illusory, inasmuch as Austrian wines, with the exception of some few of Hungarian growth, had an alcoholic force inferior to the above. As, however, the Austrian Government persisted in making the diminution of the wine tariff a sine qua non condition of the new commerci A arrangements, the English Ministers ended by adopting the step of equilizing the duty on wines, by fixing for all countries and qualities, and without any difference on. account of alcoholic strength, at Is per gallon, whether the wine be imported in casks or in bottles. The English Cabinet having entered into a formal engagement to present a Bill with that object in the next Session of Parliament, the preliminaries have been at last definitely signed at Vienna. Thus, owing to the efforts made by Austria, England is at length about to accomplish a Customs reform which was ariently demanded by the French wine producers, and which consists in assimilating the duty on wine imported in bo' ties to fhat levied on the same in cisk*. This difference of duty was an almost insurmountable obs'acle to the propagation and" consumption of French wines a nong our neighbors on the other side of the Channel. Henceforward the wine trale in France will derive from the Anglo-French Treaty of Commerce all the advantages which the Emperor's Government WiS justified in expecting."

There were 23,000 persons we'ghed on the scales at the 80-ton U.S. Mechanic's Fair. The average weight of men was 141£lb; average weight of women wa 124|1b. The largest man weighed 2931b, The largest woman weighed 274|1b.